Light-sensitive reproduction material

ABSTRACT

A PARTICULARLY STORAGE-STABLE LIGHT-SENSITIVE REPRODUCTION MATERIAL IS PREPARED BY COMBINING A PHOTO-ACTIVE ORGANIC COMPOUND SOURCE OF HALOGEN FREE RADICALS WITH A TRIPHENYLIMIDAZOLE DERIVATIVE IN A LAYER ON A SUPPORT. EXPOSURE OF THE MATERIAL TO ACTINIC LIGHT RESULTS IN THE PRINT-OUT OF A DYE. FIXING OF EXPOSED MATERIAL MAY BE ACCOMPLISHED BY HEATING OR WASHING WITH A NON-POLAR SOLVENT.

United States Patent 01 hce 3,554,754 LIGHT-SENSITIVE REPRODUCTION MATERIAL Ernst-August Hackmann, Wiesbaden-Dotzheim, Germany, assignor to Kalle Aktiengesellschaft, Wiesbaden- Biebrich, Germany No Drawing. Filed Dec. 21, 1967, Ser. No. 692,325 Claims priority, applilc(ati6olno(zllermany, Dec. 24, 1966,

rm. Cl. aim 1/72 U.S. Cl. 96-90 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION It is known that organic halogen compounds, such as tetrabromomethane or pentabromoethane, react with leucotriphenylmethane dyes upon the action of light, the latter being oxidized to give the corresponding triphenylmethane dyes. This effect has been exploited in the reproduction technique. It is described, for example, in German patent specification No. 1,134,587. The light-sensi tive material prepared in accordance therewith, however, has the disadvantage that it is storable only to a limited extent since the leucotriphenylmethane dyes oxidize relatively rapidly even in the dark. As oxidizing agents there acts the oxygen of the air as well as the halogen compounds present in the light-sensitive layer or the decomposition products thereof.

It is further known that p-hydroxy-substituted triphenylimidazoles can be oxidized to give quinoid dyes when they are exposed to light in the presence of hexaphenylbisirnidazole as an activator. But the activator is diificulty soluble in the solvents which may be used for washing out the excess of imidazole without also washing out the dyestulf formed. Also the relatively high price of the activator inhibits practical use of this light reaction.

Patented Jan. 12, 1971 SUMMARY OF THE INVENTION The present invention provides a reproduction material with a light-sensitive layer which has a good storage life in the dark, can be fixed easily, and the activator of which is easily accessible.

The invention is based upon light-sensitive reproduction material which comprises a support and a light-sensitive layer thereon containing at least one compound oxidizable to give a dyestuif upon the action of light. The reproduction material of the present invention is characterized in that the light-sensitive layer contains (1) At least one triphenylimidazole derivative of the general formula:

in which A, A, and A" may be equal or dilferent and may be OH or R R R and R may also be equal or different and may be H, alkyl, substituted alkyl, aryl, substituted aryl, halogen, nitro, amino, hydroxy, alkoxy or closed to form a mug,

(2) At least one organic halogen compound splitting oif halogen upon exposure to light.

It has been found that these layers which contain organic halogen compounds and por o-hydroxy-substituted triphenylimidazolesalso called lophinesare surprisingly light-sensitive but do not form a dyestuff when stored in the dark even after a relatively long period.

The following table indicates the main substituents, according to the above formula, of some preferably employed triphenylimidazole derivatives. The triphenylimidazole derivatives are prepared according to the general recipe by Davidson et al., J. Org. Chem, 2, 319 (1937) from the corresponding benzil, the corresponding aldehyde and ammonium acetate.

Formula II Sameasabove Br TABLE Formula A A A" Saute as above.

XII .do Same as above Ck- XIII do do Br- XVI Same as above HO The organic halogen compounds used as activators are generally readily soluble in gasoline, ligroin or similar solvents which do not or only to a small extent attack the dyestuffs formed. By washing out with the indicated solvents, the reproduction materials can easily be fixed. Such activators may also be employed as they are volatile at slightly elevated temperatures and a material is then obtained which can be fixed by simply heating, i.e. in a dry manner.

In the series of compounds generally indicated above of organic halogen compounds reacting upon exposure to light there should be particularly pointed out: tetrabromomethane, pentabromoethane, iodoform, tribromomethylphenylsulphone, and w,w,w-tribromoacetophenone which can be monoor multi-substituted in the aromatic ring by halogen, alkoxy, alkyl or nitro groups, such as 3-nitrow,w,w-tribromoacetophenone. Also tetrabromoand tetraiodopyrrole, tetraiodothiophene, and tetrabromothiophene, hexachloroethane, and tetraiodomethane are furthermore suitable. These compounds may be contained either alone or in admixture in the lightsensitive layer of the reproduction material of the present invention.

It has further been found that by the addition of ferrocene to the light-sensitive layer, sensitization of this layer for the visible range of the spectrum is achieved so that exposure to light can be carried out with incandescent lamps.

For the preparation of the reproduction material of the present invention, a solution containing one or more triphenylimidazole derivatives, one or more organic halogen compounds and, if desired, ferrocene as a sensitizer, is applied to a support and the solvent is evaporated.

Suitable support materials are wood, glass, plastics film, metal foil, textiles, and particularly cellulose derivatives, such as cellulose triacetate and paper. For better adhesion on a support having a smooth surface and for achieving thicker layers, synthetic resins, natural resins, waxes, e.g.

polystyrene, carboxymethyl cellulose, colophony, shellac, beeswax or carnauba wax may be added to the lightsensitive layers. The quantitative proportion of the individual components of the layer may vary within wide limits. Preferred results are obtained when per 0.5 to 1.5 parts by weight of organic halogen compound 0.05 to 0.3 parts by weight of imidazole derivative is employed. The ferrocene may be added in a quantity of 0.01 to 0.1 part by weight.

Coating may be performed in a usual manner by whirlcoating or spread-coating. Suitable spread-coating processes are the known immersion and roller application methods. The conditions under which the freshly spreadcoated or whirl-coated layers are liberated from the solvent depend on the evaporation properties of the solvent and of the halogen compounds. The drying temperature must be selected in a manner such that the solvent evaporates but not the halogen compound.

Processing of the reproduction material is performed in a usual manner. Exposure is carried out in contact or with lamps of strong intensity, also by projection. A visible image is obtained thereby. Preferably processed are negative originals since the reproduction material reverses the tone values and thus leads to positive copies. After exposure to light, fixation is necessary since the unexposed areas are still light-sensitive. Fixation is performed as already stated in the simplest way in that the exposed copy is washed out with a non-polar organic solvent, e.g. gasoline. After drying for a short time, the copy is ready for use. Production and use of the reproduction material of the present invention will be further illustrated by Way of the following examples.

PREFERRED EMBODIMENTS Example 1 1 g. of pentabromoethane and 0.1 g. of triphenylimidazole derivative are dissolved in 10 ml. of acetone. A baryta paper is coated with this solution. After evaporation of the 'solvent exposure to light is carried out under an original in a photoprinting machine equipped with a high-pressure mercury light source. The reproduction material passes the light source at a speed of about 1 m./min. The following table shows the colour shade of the copy. Strong copies of the original are obtained. Fixation is carried out by washing out with gasoline.

Colour shade Triphenylimidazole derivative: of the copy Forrnula I Yellow II Red III Reddish brown IV Brown V Reddish brown VI Greyish blue VII Yellow Similar results are obtained with tetrabromomethane, iodoform, 3-nitro-tribromoacetophenone, 2,5-dimethyltribromoacetophenone, tribromomethylphenylsulphone.

Example 2 As described in Example 1, baryta paper is coated with solutions and, after evaporation of the solvent, wrapped in black film and stored at room temperature. A sample is taken therefrom every month and exposed to light and fixed as described in Example 1. Even after six months, the finished copies have no background and the lightsensitivity has also scarcely decreased.

Example 3 0.8 of 3-nitro-tribromoacetophenone, 0.1 g. of triphenylimidazole of Formula HI and 0.3 g. of a maleic acid anhydride/ styrene copolymer (Lytron 820 of Monsanto) are dissolved in ml. of acetone and a baryta paper is coated with the solution. After evaporation of the solvent, exposure to light is carried out under an original in a photoprinting machine equipped with a high-pressure mercury arc lamp. The reproduction material passes the light source at a speed of about 5 m./ min. A rusty brown image of the original is obtained in the exposed areas, which can be fixed by washing with gasoline.

Example 4 l g. of tetrabromomethane, 0.2 g. of triphenylimidazole of Formula V, and 0.05 g. of ferrocene are dissolved in 10 ml. of acetone. A *baryta paper is coated with the solution and, after evaporation of the solvent, exposed for 30 seconds under an original to a 200 watt incandescent lamp and then heated for about 2 minutes to 100 C. in the drying chamber. The organic halogen compound as well as the ferrocene escape thereby so that the copy is fixed. An intensive, rusty brown, negative image of the original is obtained.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included with in the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. Light-sensitive reproduction material which comprises a support and a light-sensitive layer thereon comprising:

(a) at least one triphenylimidazole derivative of the different, at least one of said substituents being of the general formula:

l B2 I 3 l R4 R3 OH R1 with any remaining one or more of said substituents being of the general formula:

in all of which general formulae R R R R and R may be the same or different and are H, alkyl, substituted alkyl, aryl, substituted aryl, halogen, nitro, amino, alkoxy, or any two of them closed to form a ring; and

(b) at least one organic halogen compound capable of splitting oif halogen free radicals upon exposure to light; and wherein (c) the weight ratio of said triphenylimidazole to said organic halogen compound being in the range of about 0.05 to 0.3 part of said triphenylimidazole to about 0.5 to 1.5 parts of said organic halogen compound.

2. Light-sensitive reproduction material according to claim 1 wherein said layer additionally contains ferrocene.

3. Light-sensitive reproduction material according to claim 2 wherein said light-sensitive layer contains 0.05 to 0.3 part by weight of imidazole derivative and 0.01 to 0.1 part by weight of ferrocene per 0.5 to 1.5 parts by Weight of organic halogen compound.

References Cited UNITED STATES PATENTS 3,183,091 5/1965 Sporer et al 96l15X 3,370,981 2/1968 Ney et al. 117230 3,425,867 2/1969 Stillo ll7-230 WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner U.S. Cl. X.R. 96-88 

